1. Field of the Invention
The present invention is related to a channel down mixing apparatus for a car audio system, more specifically, to a channel down mixing apparatus for a car audio system having a simple structure.
2. Description of the Related Art
In recent years, as people spend much time in their cars (i.e., driving to work every weekday, traveling etc.), there are a lot of interests in safety and convenience equipments that can be mounted on the cars. One of them is a car audio system for providing better stereo sounds to passengers. Typically, a multi-channel play system, e.g., 5.1-channel play system, is used. The 5.1-channel play system reproduces respective channel sounds through five speakers that are positioned on the front side (for example, the left, right and central portions) and on the rear side (for example, the left and right portions) of a listener. The 5.1-channel play system is capable of reproducing more realistic stereo sounds by emphasizing a medium low sound band through a sub-woofer speaker.
The sub-woofer speaker can be turned on or off, depending on users' taste or favorite. The word ‘channel down mixing’ means integrating multi channels to a less number of channels, i.e., integrating a 5.1- channel sound track to 2-channel sound track, when multi speakers are not available. Another meaning of the ‘channel down mixing’ is mixing sub-woofer signals to a main channel when a user does not want the sub-woofer speaker to output sound. In the present invention, the ‘channel down mixing’ has the meaning of the later case.
However, according to a related art channel down mixing apparatus for a car audio system, the circuit used in the apparatus has a very complex structure mainly because the apparatus has a two-step buffer circuit, namely a down mixing portion and a buffer portion, and uses a separate IC to turn on/off the sub-woofer speaker, thereby increasing manufacture cost of the product. Another disadvantage of the related art apparatus is that it produces switching noise when blocking a sub-woofer signal, which is a low-frequency signal.